1. Field of the Invention
This invention relates to an improvement in a slurry hydroconversion process in which a carbonaceous feed such as a hydrocarbonaceous oil, coal or mixtures thereof, is converted to an oil in the presence of hydrogen and a metal-containing catalyst dispersed in the feed.
2. Description of the Prior Art
Slurry hydroconversion processes conducted in the presence of hydrogen and a hydroconversion catalyst dispersed in the carbonaceous feed are known. The term "hydroconversion" with reference to the oil feed is used herein to designate a process conducted in the presence of hydrogen in which at least a portion of the heavy constitutents (as measured by Conradson carbon residue) of the oil feed is converted to lower boiling hydrocarbonaceous products.
The term "hydroconversion" with reference to the coal feed is used herein to designate conversion of coal to normally liquid hydrocarbon products.
It is also known to produce metal-containing catalysts in situ in the carbonaceous feed from thermally decomposable metal compounds as well as slurry hydroconversion processes utilizing such catalysts, see for example, U.S. Pat. Nos. 4,134,825 and 4,077,867, the teachings of which are hereby incorporated by reference.
Mills' U.S. Pat. No. 3,131,142 discloses a method of removing a hydrocracking residue from a hydrocracking zone, burning the residue to obtain a metal oxide ash, reacting the metal oxide with organic acids extracted from heavy petroleum streams (i.e., naphthenic acids) in the presence of a dilute mineral acid and, thereafter, extracting the resulting metal salts of the organic acids into a hydrogen transfer diluent for subsequent use as hydrocracking catalyst.
It has now been found that in the hydroconversion upgrading of heavy hydrocarbonaceous feedstocks with a dispersed, finely divided catalyst that is prepared in situ in the process feed from a dispersed catalyst precursor compound, that effective catalysts can be formed from dispersions of aqueous solutions of oxalates of vanadium, and molybdenum and that these metals can be recovered selectively (that is, they can be recovered preferentially with respect to metals that are indigenous to most heavy feeds, such as nickel, iron, sodium and calcium) for effective reuse in the process by aqueous oxalic acid extraction of the metal-containing ash obtained when the catalyst-containing bottoms of the hydroconversion product is partially gasified to remove coke.